Multi-spectral tissue imaging

Abstract

Apparatus and methods are disclosed for multi-spectral imaging of tissue to obtain information about the distribution of fluorophores and chromophores in the tissue. Using specific spectral bands for illumination and specific spectral bands for detection, the signal-to-noise ratio and information related to the distribution of specific fluorophores is enhanced as compared to UV photography, which uses a single RGB image. Furthermore, the chromophore distribution information derived from the multi-spectral absorption images can be used to correct the fluorescence measurements. The combined fluorescence, absorption, and broadband reflectance data can be analyzed for disease diagnosis and skin feature detection.

What is claimed is: 
     
       1. A method of imaging human skin in vivo comprising:
 obtaining a fluorescence image of the human skin; 
 obtaining a cross-polarized broadband white light reflectance image of the human skin; 
 processing the cross-polarized broadband white light reflectance image to obtain a chromophore distribution image; and 
 generating a normalized fluorescence image by normalizing the fluorescence image using the chromophore distribution image. 
 
     
     
       2. The method of  claim 1 , wherein processing the cross-polarized broadband white light reflectance image includes at least one of an Independent Component Analysis (ICA) and a Principle Component Analysis (PCA). 
     
     
       3. The method of  claim 1  wherein obtaining the fluorescence image includes capturing the fluorescence image including filtering light reflected from the human skin to eliminate at least one of an ultraviolet and an infrared light. 
     
     
       4. The method of  claim 1 , wherein the chromophore distribution image includes a distribution of at least one chromophore selected from the group consisting of hemoglobin, melanin and bilirubin. 
     
     
       5. The method of  claim 1  comprising:
 storing at least one of the fluorescence image, the normalized fluorescence image, the cross-polarized broadband white light reflectance image and the chromophore distribution image; and 
 displaying at least one of the fluorescence image, the cross-polarized broadband white light reflectance image and the chromophore distribution image. 
 
     
     
       6. The method of  claim 1  comprising identifying a skin pathological condition selected from the group consisting of rosacea, hyper-pigmentation, ultraviolet light damage, melanin spots, nevi, sun tan, erythema, inflammation, irritation, and skin lesion. 
     
     
       7. The method of  claim 1  comprising:
 using at least one of the fluorescence image, the normalized fluorescence image, the chromophore distribution image, and the cross-polarized broadband white light reflectance image for:
 identifying scars and spots, 
 classifying inflammatory from non-inflammatory lesions, 
 evaluating erythema by analyzing hemoglobin information, 
 detecting wrinkles, 
 predicting future wrinkle development, 
 evaluating skin hydration levels using water absorption information, 
 evaluating at least one of a normal, dysplastic, and malignant skin lesion, 
 classifying at least one of a normal, dysplastic, and malignant lesion, 
 evaluating at least one of a skin pathology including rosacea, hyper-pigmentation, skin burn, irritation, and inflammation, 
 classifying an acne lesion as being of a type including at least one of an open comedone, closed comedone, papule, pustule, nodule, cyst, burnt-out lesion, and excoriated lesion, 
 predicting future acne lesion formation sites, 
 evaluating at least one of a treatment product and a treatment procedure; or 
 recommending at least one of a treatment product and a treatment procedure. 
 
 
     
     
       8. The method of  claim 1  comprising processing the normalized fluorescence image so as to characterize a condition of the human skin. 
     
     
       9. The method of  claim 8  comprising at least one of:
 communicating at least one of the normalized fluorescence image and the processed normalized fluorescence image; 
 storing at least one of the normalized fluorescence image and the processed normalized fluorescence image; and 
 displaying at least one of the normalized fluorescence image and the processed normalized fluorescence image. 
 
     
     
       10. The method of  claim 1 , wherein obtaining the fluorescence image includes:
 illuminating the human skin with a narrow spectral band illumination which excites a plurality of endogenous fluorophores including an endogenous target fluorophore of the human skin to each generate an emission signal; 
 filtering the emission signals so as to pass the emission signal of the target fluorophore while suppressing emissions from at least one other source; 
 capturing an image of the human skin by detecting the filtered emission signals; 
 capturing an excitation image so as to characterize a light distribution over a surface of the human skin by detecting light reflected from the human skin; and 
 normalizing the captured image using the excitation image thereby yielding the fluorescence image, 
 wherein the narrow spectral band illumination and the filtering are selected so that the filtered emission signal of the target fluorophore can be individually detected among the filtered emission signals. 
 
     
     
       11. The method of  claim 10 , wherein a wavelength range of the narrow spectral band illumination is selected so as to optimally excite the target fluorophore. 
     
     
       12. The method of  claim 10 , wherein the at least one other source includes at least one of a further fluorophore, an ambient light source, and an excitation light source. 
     
     
       13. The method of  claim 10 , wherein:
 the narrow spectral band illumination is centered around 405 nm (±15 nm), and 
 the filtering is performed with at least one of:
 a 10 to 50 nm (FWHM) narrow band-pass filter centered around 460 nm (±20 nm), for detecting a collagen fluorescence signal, 
 a 10 to 50 nm (FWHM) narrow band-pass filter centered around 560 nm (±20 nm), for detecting a horns fluorescence signal, and 
 a long-pass filter with a cut-off wavelength of approximately 620 nm for detecting a porphyrin fluorescence signal. 
 
 
     
     
       14. The method of  claim 10 , wherein:
 the narrow spectral band illumination is centered around 350 nm (±15 nm), 
 the target fluorophore includes elastin, and 
 the filtering is performed with a 10 to 50 nm (FWHM) narrow band-pass filter centered around 410 nm (±20 nm). 
 
     
     
       15. The method of  claim 1 , wherein normalizing the fluorescence image using the chromophore distribution image includes compensating for loss of at least one of an excitation and emission signal. 
     
     
       16. An apparatus for imaging human skin in vivo comprising:
 a storage device for storing instructions; and 
 a processor configured to execute the instructions to:
 obtain a fluorescence image of the human skin; 
 obtain a cross-polarized broadband white light reflectance image of the human skin; 
 process the cross-polarized broadband white light reflectance image to obtain a chromophore distribution image; and 
 generate a normalized fluorescence image by normalizing the fluorescence image using the chromophore distribution image. 
 
 
     
     
       17. The apparatus of  claim 16 , wherein processing the cross-polarized broadband white light reflectance image includes at least one of an Independent Component Analysis (ICA) and a Principle Component Analysis (PCA). 
     
     
       18. The apparatus of  claim 16 , wherein the chromophore distribution image includes a distribution of at least one chromophore selected from the group consisting of hemoglobin, melanin and bilirubin. 
     
     
       19. The apparatus of  claim 16 , wherein the processor is configured to execute the instructions to process the normalized fluorescence image so as to characterize a condition of the human skin. 
     
     
       20. The apparatus of  claim 16 , wherein the processor is configured to execute the instructions to obtain the fluorescence image by:
 controlling an image capture device to capture an image of the human skin, the human skin having been illuminated with a narrow spectral band illumination which excites a plurality of endogenous fluorophores including an endogenous target fluorophore of the human skin to each generate an emission signal, the emission signals having been filtered so as to pass the emission signal of the target fluorophore while suppressing emissions from at least one other source, and the image having been captured by detecting the filtered emission signals, wherein the narrow spectral band illumination and the filtering have been selected so that the filtered emission signal of the target fluorophore can be individually detected among the filtered emission signals; 
 controlling the image capture device to capture an excitation image that has been captured by detecting light reflected from the human skin so as to characterize a light distribution over the human skin; and 
 normalizing the captured image using the excitation image to thereby yield the fluorescence image. 
 
     
     
       21. The apparatus of  claim 20 , wherein:
 the narrow spectral band illumination is centered around 405 nm (±15 nm), and 
 the filtering is performed with at least one of:
 a 10 to 50 nm (FWHM) narrow band-pass filter centered around 460 nm (±20 nm), for detecting a collagen fluorescence signal, 
 a 10 to 50 nm (FWHM) narrow band-pass filter centered around 560 nm (±20 nm), for detecting a horns fluorescence signal, and 
 a long-pass filter with a cut-off wavelength of approximately 620 nm for detecting a porphyrin fluorescence signal. 
 
 
     
     
       22. The apparatus of  claim 16 , wherein normalizing the fluorescence image using the chromophore distribution image includes compensating for loss of at least one of an excitation and emission signal.